Abstract:

Investigation of two King Island sea caves developed in quartzitic rocks shows them to contain a wealth of clastic and chemical sediments. Clastic sediments consist of wave-rounded cobbles, debris cones, and angular rock fragments produced by frost weathering and crystal wedging. Chemical deposits include a variety of calcium carbonate speleothems and also gypsum occurring as wall crusts and blisters. The latter appear to be a speleothem type of rare occurrence. Growth of gypsum is responsible for some crystal wedging of the bedrock. Three basal stalagmite samples have been dated by the Th/U method indicating Late Pleistocene as well as Holocene speleothem growth. The caves are believed to have formed by preferential wave erosion during the Last Interglacial in altered and fractured quartzites. The evidence for pre-Holocene evolution of sea caves and geos in the Tasman region is summarised. Tasmania and the Bass Strait Islands provide a particularly favourable environment for the preservation of relict landforms on rocky coasts because of Late Quaternary uplift. The potential of further studies of sea caves to test two recently advanced archaeological hypotheses is discussed.